The man coached them their entire careers, and recruited them in high school . E has known them for 6+ years. Even if they hated the guy (which I’d assume they don’t) them saying thank you /goodbye / good luck in the future is not a bad thing.
as a coach myself (not football…) that relationship and bond is extremely powerful between players and coaches, especially when forged together through the craziness of seasons and life over many years.
id be more disappointed if they didn’t thank him for the impact he’s had on their lives, even if it ended poorly. it would imply we weren’t developing good people in addition to good players on the field.